In recent years, a facsimile apparatus and a printer controller or the like are connected to a digital copying machine that is an image forming apparatus, and one composite apparatus functioning as a copying machine, a facsimile machine, and a printer or the like is developed and generally used.
At such a composite apparatus, in general, a sleep function for automatically reducing power consumption is provided when the composite apparatus is inactive for a predetermined time.
Techniques for controlling the sleep function in such a composite apparatus are mainly divided into two sections below. That is, one is a first control technique for setting and controlling a timer for managing the sleep function to the entire composite apparatus in batch, and the other one is a second control technique for controlling a timer for managing the sleep function independently by each processing means of the composite apparatus.
In this first control technique, processing means with its use frequency as well is initiated every time processing means with its use frequency is used. Therefore, wasteful power consumption occurs. In addition, although the initiation times of processing means are different from each other, the sleep function must be controlled in batch. Therefore, a time may be set to be long according to processing means with its slow initiation or may be set to be short according to processing means with its fast initiation. In this case, if the timer is adjusted to means with its slow initiation, wasteful consumption occurs. In contrast, if the timer is adjusted to processing means with its fast initiation, operability is impaired, and startup power consumption increases.
On the other hand, in the second control method, the sleep function of each processing means is controlled completely independently. Therefore, only required processing means can be initiated and used. In addition, each timer for controlling the sleep function can be freely used according to the initiation time of each processing means.
However, in actuality, in main operation of a digital copying machine, some of the processing means of the digital copying machine main body are often used at the same time. In addition, in the case of the composite apparatus, only a printer controller or facsimile apparatus is used when changes such as settings are made through an external interface or when each item of information is computed. In general, when printer output or facsimile reception/transmission is carried out, part of processing means of the printer controller or facsimile apparatus and digital copying machine main body are used at the same time. Namely, when the operationally associated processing means is placed in a sleep state, there is a low possibility that operation is carried out.
Therefore, in view of such a circumstance, if each processing means is controlled completely independently, for example, after printer controller information is communicated through an external interface, even if all processing means of the digital copying machine main body are placed in a sleep state, there can occur a state in which only the printer controller enters a standby state without entering the sleep state. Such a state generates wasteful power consumption from the viewpoint of operation of the composite apparatus.
As an associated technique, in Jpn. Pat. Appln. KOKAI Publication No. 11-146103, in order to prevent wasteful power consumption in a copying machine, there is disclosed a technique concerning a composite apparatus for setting a predetermined time interval or a predetermined time to each of the processing means of the composite apparatus to cause each of the processing means of the composite apparatus to work the auto sleep function or the like independently.
However, in this technique, there is neither suggestion nor disclosure that operationally associated processing means are placed in synchronism with the sleep state.